To net or not to net - 3rd edition - Department of Primary Industries

More documents

Recommendations

Info

Figure 20. 12 mm quad hail net Net colour hail is possible. The tighter the stitch density, the more expensive the net and the structure required to support it. One indicator of the strength of a net is the weight per square metre (remember to compare nets of the same mesh size). Another is the thickness of the monofilament fibres, which is measured in ‘denier’. More light is intercepted by heavier, stronger nets and they have a greater impact on the orchard microclimate than lighter nets made from thinner monofilaments; however, lighter nets probably will not last as long as heavier nets. Lightweight vine net may have a weight of around 30 g/m 2 , while a 12 mm quad net typically weighs about 90 g/m 2 . In the past, other types of net have been used to protect orchards. These nets may still be available, but they are not as suitable as knitted nets for orchard netting. Extruded nets consist of a grid of extruded plastic. Extruded nets are cheap, but not as strong as knitted nets, and do not last as long. Knotted nets are made from monofilaments twisted together to form multifilament strands (rope), which are knotted together to form a square mesh net with a knot at each corner. Knotted nets are heavy and relatively expensive. Knotted nets are better than extruded nets but not as good as knitted nets. Traditionally, white nets were cheaper than black nets but had a life expectancy about two-thirds of black nets, which used carbon black as a UV stabiliser and had the best durability. However, modern white nets incorporate chemical UV stabilisers that do not colour the material and have comparable life spans to black nets. Prices are now the same or very similar for either black or white nets. White nets tend to ‘bounce’ light through the mesh and reduce light levels less than black nets with equivalent mesh size. Grey nets with properties intermediate to white and black nets are also available from some suppliers. Net width Net panel widths should coincide, if at all possible, with tree row widths or multiples of these. Panels are usually 10–15 m wide but can be specially manufactured to any width up to 50 m. Wider nets are generally favoured where available as they reduce installation costs because there is less joining; however, very wide nets can be difficult to handle when erecting. Generally speaking, a good way to determine a net’s optimum width for handling is to convert the mesh size in millimetres (not including any cross-stitch) to metres (e.g. a quad net with 12 mm mesh is best hung using 12 m wide net). With flat canopy designs, panel widths greater than 10 m may require a support wire down the centre of the panel to reduce sag. Doors Plan the position of doors carefully for efficient access. Doors can be as simple as a curtain drop of net with a pipe weight at the bottom. A more elaborate hinged-gate design, consisting of a metal frame covered with the net material, can also be used. 14 To net or not to net
An illustration of a typical netting structure is shown in Figure 21. Figure 21. A typical netting structure Basic construction procedure 1. 2. 3. 4. 5. Erect poles and anchors. Imbed corner and perimeter poles 1–1.5 m in the ground and anchors 1.5 m. In sandy soils, poles may need anti-sink pads in the bottom of the holes. Erect wire grid and tension to firm only. Thread a net wire through the net selvedging. The net does not have to be expanded to do this. In many instances, the net manufacturer will have threaded a polytube through the net selvedging to make the job of threading the wire easy. Place the bunched panels of net up onto the wire grid. Attach the net wire to the perimeter wires at both ends but do not tension them. Expand the net out to its full length (Figure 22). Figure 22. Erecting nets 6. Use C-hooks or some other type of fastener to hold the support wires of the grid close to the net wires (Figure 23). 15 To net or not to net
Page 1: To net or not to net 3rd edition By
Page 4 and 5: PR08-2008 The Department of Primary
Page 6 and 7: Other control methods 27 Financial
Page 8 and 9: Summary Orchard netting is a method
Page 10 and 11: Figure 2. Grey-headed flying fox Fi
Page 12 and 13: IMPORTANT: Do not handle sick or in
Page 14 and 15: Table 1. Results of bird/quad net t
Page 16 and 17: to investigate the problem and deve
Page 18 and 19: Pole size and quality As the struct
Page 20 and 21: The best option is to use a 6.1 mm
Page 24 and 25: Figure 23. Securing net with C-hook
Page 26 and 27: Figure 28. Nets pulled up under a w
Page 28 and 29: Figure 35. Nets over a polypipe hoo
Page 30 and 31: Table 3. Orchard microclimate chang
Page 32 and 33: Figure 43. The fruit fly (LHS) and
Page 34 and 35: evening (becoming trapped against t
Page 36 and 37: • The mesh size and quality of th
Page 38 and 39: • • • • • • • • •
Page 40 and 41: B 32 To net or not to net Figure 44
Page 56 and 57: • In addition to the primary targ
Page 58 and 59: The 2.2 ha was netted in two and a
Page 60 and 61: Figure 56. A 10 mm net with a doubl
Page 62 and 63: Case study 6—tunnel netting on ly
Page 64 and 65: Figure 63. Galvanised water pipe ca
Page 66 and 67: • • • • • • • • Pes
Page 68 and 69: Figure 69. Stone fruit under a 3.6
Page 70 and 71: • • Before the nets are put out
Page 72:
References DPI&F, Low-chill stone f
show all

To net or not to net - 3rd edition - Department of Primary Industries

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?